Recently, high-density packaging is required for the circuit board of an electronic device for the purpose of miniaturization, reduction in weight, sophistication and speeding up of the electronic device. For this reason, an electronic component and a semiconductor device (such as a chip component, a CSP (chip size package) IC) which are mounted on the circuit board is being miniaturized, reduced in thickness and speeded up and made so as to have multiterminals. As a result, a mechanical strength of the electronic component and/or the semiconductor device itself tends to be lowered, resulting in the increase in the number of the components and the devices which are weaker against mechanical stress and temperature change to which they are exposed. Further, the trend of the high-density packaging causes a more cost per electronic component and/or the semiconductor device and a more cost per circuit board on which the electronic parts are mounted.
A method for mounting an electronic component and/or a semiconductor device on a circuit board is commonly carried out, which includes:
positioning an electronic component and/or a semiconductor device at a predetermined position on a circuit board so that the corresponding electrodes are contacted,
supplying a solder material or a conductive adhesive between the electrodes to be connected,
connecting the electrodes of the electronic component and/or the semiconductor device to the electrodes of the circuit board in a reflow furnace, and
sealing an area between the electronic component and/or the semiconductor device and the circuit board including connections with a resin, before or after, or in parallel with the connecting operation. This resin sealing is important for securing the electronic component and/or the semiconductor device to the circuit board even if the circuit board is exposed to heat cycle or an environment of high humidity and high temperature, and for protecting the connections between the electronic component and/or the semiconductor device and the circuit board with high reliability.
Patent Literature 1 (particularly in paragraph 0032) discloses an invention wherein a low elastic-modulus adhesive for electronic parts is used to reduce the thermal stress between the electronic parts and a wiring board. The purpose of the invention is to ensure the reliability of the circuit board on which the electronic parts are mounted when it is exposed to the heat cycle. This patent literature focuses on a point that the thermal stress occurs when the circuit board is exposed to the heat cycle because of difference between a thermal expansion coefficient of the semiconductor chip and that of the circuit board, and discloses that it is effective to use the low elastic-modulus adhesive for electronic parts in order to reduce the thermal stress.
In general, inspection or test (herein after, they are referred to collectively as “inspection”) is conducted in a plurality of assembling stages in an assembling process of an electric appliance so as to detect faulty products (or off-specification products), and off-specification products that have been detected are excluded from the assembling process. Further, the product which is admitted as an on-spec product is sent to a subsequent assembling process so as to be used in the production of the electric appliance. In the case where the circuit board on which the electronic component and/or the semiconductor device is mounted (herein after, it is referred to as a “mounting-completed circuit board”) is determined to be the off-specification product, discarding the mounting-completed circuit board as a whole leads to increase in the cost of the final product because the cost of each of the electronic component and/or the semiconductor device and the mounting-completed circuit board is high. Further, this discarding also leads to increase in the volume of industrial waste. For these reasons, such discarding is not desirable in that it imposes burdens on the producer, consumers and the environment.
The mounting-completed circuit boards determined to be off-specification products include electronic components and/or the semiconductor devices that are damaged by various causes including exposure to heat. In the case where many electronic components and/or many semiconductor devices are mounted on a single circuit board and one or a few of them are faulty (or do not comply with the specification) and the others are not damaged themselves, removing the electronic components and/or semiconductor devices which are determined as the faulty products (or off-specification products) and replacing them with normal ones make it possible to utilize the remaining parts of the mounting-completed circuit board as long as the faulty ones can be removed easily. Therefore, it is desirable, from the view points of cost reduction and the demands of the times such as resource saving and emission free (environmental protection), that only the faulty electronic components and/or faulty semiconductor devices are removed from the mounting-completed circuit board determined as off-specification products and the remaining electronic components and/or the semiconductor devices and the circuit board which retain necessary functions are recovered and/or the recovered ones are recycled. In should be noted that, with respect to the present invention, recovery and/or recycle of at least one of the circuit board, the electronic components and the semiconductor devices (these are also referred to as “board goods” hereinafter) is referred to as “repair” of the board goods.
For example, Patent Literatures 2 and 3 disclose that a resin having repairability is used for sealing so that the mounting-completed board can be recycled by repairing faulty electronic components and/or semiconductor devices when fault is found in one or several electronic components and/or semiconductor devices from a large number of components and/or devices mounted on the circuit board during the inspection which is made after mounting and sealing processes are completed. Further, Patent Literature 4 suggests a technique of removing the resin remaining on the circuit board by applying an adhesive having a higher strength to the resin followed by heating and detaching the resin with a plate for detachment. Furthermore, Patent Literature 5 suggests a technique of removing the resin remaining on the board with a grinding cutter.